"
Watershed": Medical Usage
This is a term used to describe a specific type of stroke based on its appearance on a CT (computed tomography) scan.
In general, specific arteries supply specific parts of the brain with blood. Most strokes are caused by a blockage or rupture of one of these arteries.
"Watershed" strokes are found in areas of the brain where two arteries (analagous to "rivers") diverge, each one supplying that portion of brain with oxygen-rich blood.
During a catastrophic event like a cardiac arrest or prolonged surgery, the blood pressure may drop to the point that blood fails to circulate to the brain. Some areas are more vulnerable to hypotension than others, particularly those that are between two arteries, hence the term "watershed infarct."